So no matter what method we use, chocolate should always be melted with gentle heat because it scorches easily. If chocolate is to be melted alone, make sure that the boiler and stirring utensil are dry cause even a tiny drop of moisture will cause the chocolate to become lumpy and stiff, which we don't want ever to happen.

Over very low heat:

Place unwrapped and chopped chocolate in a small saucepan over very low heat. Stir constantly until everything's melted and smooth. Remove from heat.

Over hot water (my most used method):

Place unwrapped and chopped chocolate in top of double boiler. Melt over hot (not boiling) water, stirring constantly until smooth, about 10 to 12 minutes.

In liquid:

Chocolate may be melted with butter or liquid (milk/cream) as the recipe calls over very low heat directly, stirring constantly. Continue stirring until thoroughly blended and smooth.

In a Microwave oven:

Place chocolate buttons or chopped chocolate in a microwable bowl or dish and heat for about 1 to 2 minutes. Remove from microwave and stir. Put the bowl back inside the microwave and heat for another 10 seconds. Remove and stir. Continue the process until smooth.

For Dip and glaze:

Place the chocolate over how water and heat only until partially melted, remove from water and stir until chocolate is entirely melted. This will keep the chocolate glossy.

Here are just few methods I know. There'd be a lot more in other sources. But still, I hope this helps! Adios! :D